More than 60 New Jersey high school seniors were arrested early Thursday after they allegedly broke into their school for a class prank overnight, urinating in the hallways, flipping desks and greasing door handles, police say.

Police responded to a burglary alarm at Teaneck High School shortly before 2:30 a.m. When they arrived, several students tried to run away but officers found dozens of teens still there, some hiding, and significant damage throughout the school, according to Teaneck Police Sgt. John Garland.

Garland said officers found balloons throughout the building, flipped desks, petroleum jelly on doorknobs and urine in the hallways. Police also watched some of the alleged criminal activity on the closed-circuit security system as it was happening.

“I’ve been a police officer 19 years, and this is the craziest thing I’ve ever seen,” Garland said.